1. Field of the Invention
The present invention relates to a method and apparatus for a vehicle liftgate and a hinge assembly associated with the liftgate that includes a torsion rod as the hinge pin journaled within the hinge leafs for selective torsion application.
2. Background Art
The construction of a movable vehicle liftgate, for example, a closure panel at the rear of the passenger compartment of a sport-utility style body type, raises challenges for vehicle manufacturers. The interior as well as the exterior surfaces must be compatible with the adjacent interior compartment and exterior compartments of the vehicle. In addition, the mounting mechanism may be concealed for aesthetic purposes, but the panel must be stable in upright and lowered positions. As a result, any attempt to make the panel displaceable, for example, a pivot axis mounting, preferably one that includes lift assist, must be compactly packaged without affecting the aesthetic appearance, access or the functionality of the panel. For example, previously known mechanisms for displacing liftgates use gas-powered struts to bias the liftgate toward a raised position. However, the axis of the struts, and the line force exerted by the struts, may not be aligned to exert substantial force at initial opening from the closed position. Accordingly, a substantial force must be exerted by a person operating the liftgate to open the liftgate.
A previously known tailgate mounting unit that permits pivoting of the tailgate between upright (closed) and horizontal (open) positions. The hinge assembly uses a torque rod and first and second hinge sets at spaced apart positions. However, while the long torque rods extends through spaced hinge sets, such constructions lack self containment of the hinge sets and require adjacent support and pivot structures because the tailgate fits between body panels. As a result, the hinge structures are not so readily incorporated with liftgates.
Another known vehicle closure hinge design that employs lift assistance in the form of coiled or clock spring type torsion devices are expensive to construct and generate such problems such as cycle noise and poor cycle life, due to binding between the numerous coils of the torsion spring structure in the panel mounting assembly. Moreover, many previously known self-contained hinges with torque rods and spring designs do not provide a sufficient length of wire in which torsion energy can be generated to displace opposite ends of the torsion rod and thus the leaf members of the hinge set, when the hinge parts are mounted to large or massive structures. Moreover, previously known vehicle panel hinges with torque rods exert a biasing force at both limits of the travel path of the panel between open and closed positions.